A barcode containing a serial number, lot number, or other identifying code has conventionally been imprinted on optical discs as a means of identifying whether a disc is an authorized disc or a pirated copy.
A method for recording barcode-shaped marks (below a “BCA mark”) to a burst cutting area (BCA) and reading this BCA mark with the optical head of the optical disc playback drive has been proposed and implemented for use with DVD media in particular.
Prepits and pregrooves are formed in the BCA of DVD media at the same track pitch used in the read-only area where read-only data is recorded and in the read-write area that is both readable and writable. A problem with write-once and read/write discs is the danger of the BCA mark in the BCA being erased or altered by the read/write drive. Tampering with the BCA mark during the production of pirated copies is a particular problem because legal copies and pirated copies cannot then be distinguished.
Furthermore, if pregrooves and prepits are not formed in the BCA where the BCA mark is recorded, that is, if the BCA is a mirror surface area, the optical head cannot track properly for the detection and playback of the barcode-shaped BCA mark recorded in the BCA. In this case the optical head can only be positioned to the precision of the drive mechanism used to move the optical head. The average user, however, could use various types of drives, and it is therefore necessary to employ a design that accounts for variation between different drives.
An object of the present invention is therefore to make tampering with the BCA mark difficult in an optical disc or other optical recording medium while enabling a barcode-shaped BCA mark in the BCA to be reproduced with tracking control.